1. Field of the Invention
This invention generally relates to a coil spring assembly. More specifically, the present invention relates to a coil spring assembly provided with spring seats arranged on opposite ends of each coil spring.
2. Background Information
A damper mechanism used in a clutch disk assembly of a vehicle includes an input rotary member, an output rotary member and an elastic coupling mechanism. The input rotary can be coupled to an input flywheel. The output rotary member is coupled to a shaft extending from a transmission. The elastic coupling mechanism elastically couples the input and output rotary members together in a rotating direction. The input rotary member includes a clutch disk and a pair of input plates fixed to a radially inner portion of the clutch disk. The output rotary member includes a hub, which is nonrotatably coupled to the shaft. The hub includes a boss engaged with the shaft via a spline, and a flange extending radially outward from the boss. The elastic coupling mechanism includes a plurality of coil springs. Each coil spring is disposed within a window formed in the flange. Each coil spring is supported within square windows formed in a pair of input plates. When the pair of input plates rotates relatively to the hub, the coil springs are compressed between the plate pair and the hub in the rotating direction. The damper mechanism absorbs and dampens torsional vibrations in the rotating direction which are supplied to the clutch disk assembly.
Usually, the coil spring has end surfaces, which are finished into flat forms by grinding the end turns, respectively. Thereby, the end surface of the coil spring can reliably be in contact with the paired input plates and the window edge of the hub flange. However, the ground end is easily chipped.
When the coil spring is compressed in the rotating direction, the radially outer portion is compressed by an amount larger than the radially inner portion. This is due to the fact that a radially outer portion of the square windows or the like engaged with the coil spring moves a larger amount in the rotating direction than a radially inner portion. As a result, a radially inner wire portion, which absorbs deflection of the radially outer portion, is deformed by a larger amount than a radially outer wire portion. Therefore, the radially inner wire portion is subjected to a larger stress. Since the stress generated in each spring is variable depending on the positions, the life span of the coil spring is relatively short.
In view of the above, there exists a need for coil spring assembly and damper mechanism that overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
An object of the invention is to increase the life span of a coil spring used in the damper mechanism.
According to one aspect of the present invention, a coil spring assembly is used in a damper mechanism for transmitting a torque and dampening torsional vibrations. The coil spring assembly includes a coil spring and a pair of spring seats. The coil spring has end turns not subjected to grinding. Each of the paired spring seats has a seat surface in contact with a whole end turn. According to the coil spring assembly of this aspect of the present invention, the coil spring has an end turn, which is not subjected to a grinding process. Furthermore, the paired spring seats support the unground end turns, respectively. Therefore, breakage of the coil spring end can be suppressed.
According to another aspect of the present invention, the coil spring assembly of the aforementioned aspect of the present invention further has a feature such that each of the paired spring seats has a contact surface. Each contact surface is in contact with an end surface of the end turn. Thereby, the coil spring cannot rotate with respect to the spring seat around a central axis of the spring toward the contact surface. In other words, the paired spring seats do not rotate around the central axis of the spring. This prevents rotation of the coil spring with respect to the damper mechanism.
According to another aspect of the present invention, the coil spring assembly of the previous aspect of the present invention further has a feature such that each of the paired spring seats further has an engagement portion. The engagement portion is engaged to prevent rotation with respect to the damper mechanism around the central axis of the coil spring when arranged in the damper mechanism. Therefore, the coil spring does not rotate relatively to the damper mechanism around the spring central axis. Thus, the radially outer portion and the radially inner portion of the coil spring do not change places with each other. Accordingly, the coil spring, whose radially inner portion includes a larger number of turns than those of the radially outer portion, can be arranged in the damper mechanism. This relationship with respect to the number of turns can be maintained. Thereby, it is possible to reduce a difference in the amount of deformation per turn between the radially inner and outer portions of the spring in the compressed state. Thus, it is possible to reduce a difference in stress generated per turn between the radially inner and outer portions of the coil spring.
According to another aspect of the present invention, a damper mechanism includes an input rotary member, an output rotary member and a coil spring assembly. The coil spring assembly is provided for elastically coupling the input rotary member and the output rotary member together in a rotating direction. The coil spring assembly has a coil spring and a pair of spring seats. The paired spring seats are engaged with ends of the coil spring such that the coil spring is nonrotatable around its central axis relatively to the spring seat. The paired spring seats are engaged with the input and output rotary members. The paired spring seats are nonrotatable relatively to the input and output rotary members around the central axis of the coil spring. According to the damper mechanism of this aspect of the present invention, the paired spring seats prevent the coil spring from rotation around its central axis with respect to the input and output rotary members. Thus, the radially inner portion and the radially outer portion of the coil spring do not change places with each other. Accordingly, the coil spring, whose radially inner portion includes a larger number of turns than those of the radially outer portion, can be arranged in the damper mechanism. This relationship with regard to the number of turns can be maintained. Thereby, it is possible to reduce a difference in the amount of deformation per turn between the radially inner and outer portions of the spring in the compressed state. Thus, it is possible to reduce a difference in stress generated per turn between the radially inner and outer portions of the coil spring.
According to another aspect of the present invention, the damper mechanism of the previous aspect of the present invention further has a feature such that, in the radial direction of the damper mechanism, the turns on the inner side of the coil spring are larger in number than those on the outer side of the coil spring.
According to another aspect of the present invention, a coil spring assembly is used in a damper mechanism for transmitting a torque and dampening torsional vibrations. The coil spring assembly includes a coil spring and a pair of spring seats. The coil spring has end turns. Each of the paired spring seats has a seat surface and a contact surface. The seat surface is in entire contact with the end turn. The contact surface is in contact with the end surface of the end turn such that the coil spring is nonrotatable around its axis. Thereby, the coil spring cannot rotate with respect to the spring seat around the spring central axis toward the contact surface. Thus, by preventing the rotation of the paired spring seats around the spring central axis, the coil spring cannot rotate with respect to the damper mechanism.
According to another aspect of the present invention, the coil spring assembly of the previous aspect of the present invention further has a feature such that each of the paired spring seats further has an engagement portion. The engagement portion is engaged to prevent rotation with respect to the damper mechanism around the central axis of the coil spring when arranged in the damper mechanism. Therefore, the coil spring does not rotate relatively to the damper mechanism around the spring central axis. Thus, the radially outer portion and the radially inner portion of the coil spring do not change places with each other. Accordingly, the coil spring, whose radially inner portion includes a larger number of turns than those of the radially outer portion, can be arranged in the damper mechanism. This relationship regarding the number of turns can be maintained. Thereby, it is possible to reduce a difference in the amount of deformation per turn between the radially inner and outer portions of the spring in the compressed state. Thus, it is possible to reduce a difference in stress generated per turn between the radially inner and outer portions of the coil spring.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention.